I've made the question below in https://forum.primefaces.org/viewtopic.php?f=3&t=51091, and the Primefaces Core Developer Thomas Andraschko give me a hint to try getting answers here ("Try to ask the hibernate validator guys. It seems like it uses getter and the property and those types doesn't match").

Even so, seems like Hibernate Validator should have used field access in your example.Please share the version of Hibernate Validator you're using, to see if we need to create a new bug in our issue tracker.